Weird MIDI silence during playback only

So all of a sudden last night, while working on an inspired track, the playback just stopped producing sound on a MIDI track.

I could still play into the track (a Woombat in Retrologue), could also still hear the note when clicking on them in the midi editor. No record ability or sound otherwise. I could still see MIDI information coming into Cubase. Tried changing the monitoring, copying and pasting to a new track, starting a new instrument track - nothing.

Has anyone encountered something like this before?

Will try again starting from scratch again at home later this evening.